Muwatta Malik Book 8, Hadith 18
Yahya related to me from Malik from Hisham ibn Urwa from his
father that A'isha, the wife of the Prophet, may Allah bless him and
grant him peace, said, "The Messenger of Allah, may Allah bless him
and grant him peace, prayed while he was ill. He prayed sitting, and
some people prayed behind him standing, and he indicated to them to
sit down. When he left, he said, 'The imam is only appointed to be
followed. When he goes into ruku, go into ruku and when he rises, rise
and if he prays sitting, pray sitting .' "
Yahya related to me from Malik from Ibn Shihab from Anas ibn Malik that the Messenger of Allah, may Allah bless him and grant him peace, fell off his horse when riding, and his right side was scraped, so he did one of the prayers sitting, and we prayed behind him sitting. When he left, he said, "The imam is appointed to be followed. If he prays standing, then pray standing, and when he goes into ruku, go into ruku, and when he rises, rise, and when he says, 'Allah hears whoever praises him,' say, 'Our Lord, praise belongs to You,' and if he prays sitting, then all of you pray sitting."
Yahya related to me from Malik from Hisham ibn Urwa from his father that the Messenger of Allah, may Allah bless him and grant him peace, came out during his illness, and approached and found Abu Bakr standing, leading the people in prayer. Abu Bakr began to go back, but the Messenger of Allah, may Allah bless him and grant him peace, indicated to him to stay where he was. The Messenger of Allah, may Allah bless him and grant him peace, sat by the side of Abu Bakr, and Abu Bakr prayed following the prayer of the Messenger of Allah, may Allah bless him and grant him peace, who was sitting, and the people prayed following the prayer of Abu Bakr.